Extraction methods and systems for recovery of oil from reservoirs containing mobile water

ABSTRACT

The present disclosure relates to, according to some embodiments, an extraction process for recovering an oil from an oil reservoir comprising a mobile water. The extraction process includes the step of injecting a first solvent into the oil reservoir through the at least one injection well to form a first mixture, the first mixture comprising the first solvent, a first portion of mobile water, and a first portion of oil. Additionally, the extraction process includes the steps of recovering the first mixture from the at least one production well to produce a first recovered oil mixture, the first recovered oil mixture comprising the first solvent, the first portion of the mobile water, and the first portion of oil; separating the first recovered oil mixture to produce a first recovered oil fraction that is separated from the first portion of mobile water and the first solvent; and injecting a second solvent into the oil reservoir through the at least one injection well to form a second mixture, the second mixture comprising the second solvent, a second portion of mobile water, and a second portion of oil. The extraction process also includes the steps of recovering the second mixture from the at least one production well to produce a second recovered oil mixture, the second recovered oil mixture comprising the second solvent, the second portion of the mobile water, and the second portion of oil, and separating the second recovered oil mixture to produce a second recovered oil fraction that is separated from the second portion of mobile water and the second solvent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional ApplicationNo. 16/120,965, filed on Sep. 4, 2018, which claims priority to U.S.Provisional Application No. 62/599,439, filed Dec. 15, 2017, and alsoclaims priority to U.S. Provisional Application No. 62/554,716, filedSep. 6, 2017. The contents of all of the above are hereby incorporatedin their entirety by reference.

BACKGROUND

Oils refer to crude oils which have high specific gravity and viscosityand are therefore difficult to extract commercially because they do notreadily flow. Typically, these oils will have viscosities greater than1000 mPa.s (centiPoise) or specific gravities greater than 0.934 kg/m³at 15.5° C. (60° F.) (i.e. less than 20 API). Oil wet reservoirs are oildeposits where the oil is the rock wetting fluid. Typically, thesereservoirs have poorer recoveries due to the oil's strong adherence tothe reservoir rock. There has long been sought a means to accelerate oilproduction processes by permitting the oil to flow more readily therebyincreasing the rate of return on capital and decreasing the financialrisk of such oil production projects.

One approach to oil extraction involves the use of steam in a thermalstimulation to facilitate oil extraction. Steam raises the temperatureof the oil and thereby reduces its viscosity and allows it to flow moreeasily. The two main traditional approaches used in steam recoverysystems have been “huff and puff” (i.e., cyclic steaming) and steamfloods. Steam stimulation is subject to a number of problems, includingheat losses during injection, clay swelling problems, thief zones,emulsions, capillary surface tension effects and lack of confinement forshallower zones. Further, injecting steam creates water (condensate) inthe formation which is much less viscous than oil and which willtherefore be preferentially produced due to relative permeabilityeffects. Preferential production of water makes the oil production orrecovery more difficult.

Another approach to oil extraction is steam assisted gravity drainage(SAGD). SAGD begins with the formation of a steam chamber in theformation. The steam is injected at the chamber surface. The heated oilflows down the walls of the chamber under the influence of gravity anddrains into the production well, thereby increasing the size of thechamber. SAGD employs the countercurrent flow of steam upwards into thereservoir and oil down and out of the reservoir, which in certainsituations can be relatively efficient, and provide oil production rateshigh enough to provide favorable economics. There are many possible SAGDgeometries including single well (injection and production from the samewell) and dual or multiple well. The wells may be either horizontal orvertical. Generally horizontal wells are favored by producers becausethey offer a greater (longer) exposure to the pay zone and thereby offerincreased production rates for highly viscous oils.

Yet another approach is the vapor extraction (VAPEX) process, whichproposes to combine a heated solvent (propane) with hot water heated atsurface to provide downhole heat. Because of the use of hot water, thisprocess suffers from the problems mentioned above (countercurrent heatexchange, formation damage problems with clays, emulsions, capillarypressure, water treatment, water supply, reduced oil relativepermeability due to high water saturations and the like).

Oil wet reservoirs often require surfactants to alter the wettability ofthe reservoir. When added to a flooding mechanism, the oil can beremoved in a more typical fashion. Unfortunately, incorrect applicationof surfactants can damage a reservoir beyond repair.

Existing heated solvent processes and Steam-assisted Gravity Drainage(SAGD) processes have typically been avoided for extraction fromreservoirs that contain mobile water, as the mobile water has beenthought to be detrimental to all forms of enhanced oil recovery (EOR).Thin pay zones have not been considered for SAGD due to associated highheat losses to the surrounding rocks.

In addition, existing heated solvent processes do not work in thecarbonate reservoirs due to substantially higher reservoir pressurerequired which precludes the use of condensing vapor or condensingsolvent processes. Moreover, the use of heated propane as the solvent,as used in processes like the VAPEX process, can cause asphalteneplugging of the well, resulting in a substantial loss of recoverableoil. Further, surfactants typically are cost ineffective due to rockabsorption rates.

While the application of heat or chemicals, either directly to thereservoir or via the injection of heated solvents, has a demonstratedeffect in mobilizing oil for extraction, each of the above processessuffers from the disadvantage of having either high energy requirementsfor the generation of the steam and/or heated solvents or a damagingreaction. The energy requirements are typically met through the burningof large amounts of fuel, usually natural gas. This leads to theemission of enormous amounts of greenhouse gases such as carbon dioxide.For example, a 100,000 barrels (bbl) of oil per day SAGD facilityrequires 200,000-300,000 bbl water per day to be converted into steam.Thus, to recover 100,000 bbl oil per day using a natural gas burnersystem results in producing more than 12 million pounds per day ofcarbon dioxide emissions.

Therefore there is a need for an energy efficient and cost effectiveprocess for stimulating production of oil, and which does not sufferfrom the aforementioned problems, such as asphaltenedeposition/plugging.

BRIEF SUMMARY

In one embodiment, an improved extraction process for recovering oilfrom an oil reservoir containing mobile water is described. Theextraction process establishes at least one injection well and at leastone production well. A first solvent may be injected into the oilreservoir through the injection well to form a combined first solventand oil mixture. A first solvent may be miscible in the oil whilecarried to the oil by the first solvent. The combined first solvent andoil mixture may be recovered from at least one production well toproduce a first recovered oil fraction and first solvent mixture. Theextraction process may then separate the first recovered oil fractionand first solvent mixture to produce a first recovered oil fraction anda separated first solvent. A second solvent may be injected into the oilreservoir through the injection well (or another injection well) to forma combined second solvent and residual oil mixture. The combined secondsolvent and residual oil mixture may be recovered from the productionwell (or another production well) to produce a second recovered residualoil fraction and second solvent mixture. The recovered residual oilfraction and second solvent mixture may be separated to produce a secondrecovered oil fraction and a separated second solvent.

In some embodiments, the first recovered oil fraction and the secondrecovered oil fraction may be combined to produce a combined recoveredoil fraction, wherein the combined recovered oil fraction may comprise ayield from about 50% to about 100%. The first solvent may be at atemperature from about 10° C. to about 40° C. during the step ofinjecting the first solvent into the oil reservoir through the at leastone injection well. The second solvent may be at a temperature fromabout 10° C. to about 40° C. during the step of injecting the secondsolvent into the oil reservoir through the at least one injection well.The first solvent and the second solvent may be at the temperature ofthe oil reservoir.

In some embodiments, the first solvent may comprise a methane, anethane, a propane, a butane, a pentane, a hexane, terpenes, benzene,toluene, aromatic hydrocarbons, water, and combinations thereof. In someembodiments, the second solvent may comprise a terpene or combination ofterpenes, a turpentine, an alcohol, an aromatic hydrocarbon, water, andcombinations thereof. The second solvent may comprise at least onediverting agent. The diverting agent may be selected from the groupconsisting of a viscous surfactant, a polymer, a CO₂, and an acid. Thediverting agent may be present at a concentration from about 0.01% toabout 50%, by volume of a second solvent.

In another embodiment, an extraction process according to the presentdisclosure may include injecting a first solvent into the oil reservoirthrough the at least one injection well to form a first mixture, thefirst mixture comprising the first solvent, a first portion of mobilewater, and a first portion of oil. The extraction process may furtherinclude injecting a second solvent into the oil reservoir through the atleast one injection well to form a second mixture, the second mixturecomprising the second solvent, a second portion of mobile water, and asecond portion of oil. The extraction process may further includeinjecting water into the oil reservoir through the at least oneinjection well to form a flooded injected water and oil mixture. Thewater may be a water exogenous to the oil reservoir, or a waterrecovered from the oil reservoir, or a combination thereof. The watermay be injected into the oil reservoir through the at least oneinjection well after injecting the second solvent into the oil reservoirthrough the at least one injection well.

BRIEF DESCRIPTION OF THE DRAWINGS

The file of this patent contains at least one drawing executed in color.Copies of this patent with color drawings will be provided by the Patentand Trademark Office upon request and payment of the necessary fee.

Exemplary embodiments of the present disclosure are described hereinwith reference to the drawings, wherein like parts are designated bylike reference numbers, and wherein:

FIG. 1 illustrates an extraction process for recovering an oil from anoil reservoir according to a specific example embodiment of thedisclosure;

FIG. 2 illustrates a system for extracting oil from an oil reservoiraccording to a specific example embodiment of the disclosure;

FIG. 3 illustrates a graphical representation of an oil recovery withmobile water and without mobile water according to a specific exampleembodiment of the disclosure;

FIG. 4 illustrates a graphical representation of an oil recovery withmobile water and without mobile water according to a specific exampleembodiment of the disclosure;

FIG. 5 illustrates oil recovery based on well configuration according toa specific example embodiment of the disclosure;

FIG. 6A illustrates a thief water zone according to a specific exampleembodiment of the disclosure; and

FIG. 6B illustrates a thief water zone according to a specific exampleembodiment of the disclosure.

DETAILED DESCRIPTION

The present disclosure relates, in some embodiments, to an extractionprocess for recovering oil from an oil reservoir or reservoir thatincludes oil and mobile water. The extraction process utilizes a firstsolvent and a second solvent, or a combination thereof, which may beprovided to or injected into the oil reservoir at an injection well. Thefirst and second solvent may be injected at a reservoir temperature, ata reservoir pressure, above reservoir pressure. According to someembodiments, an extraction process using a first solvent and a secondsolvent may desirably provide for a greater recovered oil fraction incomparison to a corresponding extraction process not having the firstsolvent and the second solvent. The extraction process described hereinusing a first solvent and a second solvent may desirably provide for adisplacement of mobile water within an oil reservoir, which may increasepropagation, diffusion, contact, or a combination thereof, of the firstsolvent or the second solvent with the oil. The first solvent, thesecond solvent, the oil, the water, or combinations thereof, may berecovered through one or more production wells.

As discussed above, the first solvent and the second solvent may beinjected into the oil reservoir at one or more injection wells at areservoir temperature or the temperature of the oil reservoir. Forexample, since an oil reservoir may have a temperature from about 10° C.to about 40° C., a first solvent, a second solvent, or a combinationthereof, may be injected into the oil reservoir at a temperature fromabout 10° C. to about 40° C. By injecting the first and/or secondsolvent at the oil reservoir temperature, the extraction process mayadvantageously increase a yield of a recovered oil fraction.

Example embodiments are shown in FIGS. 1-6B. FIG. 1 illustrates anextraction process for recovering an oil from an oil reservoircontaining mobile water. FIG. 2 illustrates a system for extracting oilfrom an oil reservoir. FIG. 3 illustrates a graphical representation ofan oil recovery with mobile water and without mobile water according toa specific example embodiment of the disclosure. FIG. 4 illustrates agraphical representation of an oil recovery with mobile water andwithout mobile water. FIG. 5 illustrates oil recovery based on wellconfiguration. FIGS. 6A and 6B illustrate a thief water zone accordingto a specific example embodiment of the disclosure.

FIG. 1 illustrates an extraction process 100 for recovering oil from anoil reservoir containing mobile water. The extraction process 100 maycomprise the steps of a) establishing one or more injection wells andone or more production wells 110, b) injecting a first solvent into theoil reservoir through the at least one injection well to form a firstmixture, the first mixture comprising the first solvent, a first portionof mobile water, and a first portion of oil 120, recovering the firstmixture from the at least one production well to produce a firstrecovered oil mixture, the first recovered oil mixture comprising thefirst solvent, the first portion of the mobile water, and the firstportion of oil 130; (d) separating the first recovered oil mixture toproduce a first recovered oil fraction that is separated from the firstportion of mobile water and the first solvent 140, and recovering thefirst recovered oil 145. Additionally, the process may include a step ofrecycling the separated first solvent 135.

The above described extraction process 100 also includes the steps of(e) injecting a second solvent into the oil reservoir through the atleast one injection well to form a second mixture, the second mixturecomprising the second solvent, a second portion of mobile water, and asecond portion of oil 150; (f) recovering the second mixture from the atleast one production well to produce a second recovered oil mixture, thesecond recovered oil mixture comprising the second solvent, the secondportion of the mobile water, and the second portion of oil 160; and (g)separating the second recovered oil mixture to produce a secondrecovered oil fraction that is separated from the second portion ofmobile water and the second solvent 170. The second recovered oilfraction may comprise reservoir water. The combined recovered oilfractions may provide for a yield from about 50% to about 100%. Theyield may include percent oil contained in the oil reservoir at theinitiation of the oil recovery process. For example, the combinedrecovered oil fractions may provide for a yield from about 50% to about90% of the oil present in the oil reservoir prior to the extractionprocess, within the first 10 years of oil recovery, but mayincrementally increases to a complete recovery, or a yield of 100%, overa 25 year period. The first recovered oil fraction and the secondrecovered oil fraction may be combined 190. Additionally, the separatedsecond solvent may be recycled 165.

The injecting of the first solvent into the oil reservoir 120 and theinjecting of the second solvent into the oil reservoir 150 may beperformed iteratively, concurrently, and sequentially. In someembodiments, the second solvent may not be used. In other embodiments,the first solvent may be injected and then the second solvent may beinjected into the oil reservoir. The second solvent may desirablyprovide for asphaltene dissolution, which may mitigate an effect ofasphaltene deposition. In some embodiments, the first solvent may becombined with the second solvent and then the combined solvent mixturemay be injected into the oil reservoir. The first solvent and the secondsolvent may be mixed at various ratios and then injected into the oilreservoir. For example, the ratio of first solvent to second solvent mayinclude from about 1:99 to about 1:1. Additionally, the ratio of firstsolvent to second solvent may include from about 1:1 to about 99:1.

The first solvent and the second solvent may be injected into the oilreservoir at a temperature from about 10° C. to about 40° C. and at apressure from about 50 kPa to about 1500 kPa above original reservoirpressure. Additionally, the extraction process may proceed without theuse of surfactants, where the use thereof may require additionalpurification steps to remove the surfactants from the final oilproduct(s). Therefore, the extraction process 100 described above maydesirably provide for advantages over conventional processes, theadvantages including higher recovered oil yields, lower capitalrequirements, solvent injections operating below fracture pressure, andmaintenance of overall reservoir pressure. Also, the dual solventextraction process 100 described above may displace mobile reservoirwater and propagate deep within the oil reservoir, which may provide fora higher yield of recovered oil contacted by the mobile water that wouldbe otherwise inaccessible to conventional processes.

The extraction process 100 may be suitable for extracting oil, includinga heavy oil and a light oil, from oil reservoirs such as carbonate rockdeposits (e.g., dolomite or limestone reservoirs) and oil wetreservoirs, but may also be used in other formations such as oil sandsdeposits. The hybrid cold solvent process 100 may employ combinations ofsolvents that can be optimized for water wet, oil wet, and fractionallywet reservoirs.

The above described extraction process 100 may also include a waterflooding or water injection stage. Water injection prior to solventinjection may be desirable in some cases where mobile flow pathwaysbetween the injection well and the production well are not available.Water may also be injected into the oil reservoir after the step ofinjecting the second solvent into the oil reservoir 150; and after thestep of recovering the combined second solvent/ oil mixture 160. Waterinjection may be done with fresh water or by mobile water recovered fromthe extraction process 100. Late water injection may be a viable solventinjection step.

The separation of the first recovered oil mixture to produce a firstrecovered oil fraction that is separated from the first portion ofmobile water and the first solvent 140 or the separation of the secondrecovered oil mixture to produce a second recovered oil fraction that isseparated from the second portion of mobile water and the second solvent170 may also include purifying the first solvent or the second solvent.The separation may include separation from water and then recovering thesolvent from the produced oil. The water may be recovered mobile water.For example, the recovered first solvent or recovered second solvent maybe distilled before recycling them back into the extraction process 100.

The extraction process described above 100 may facilitate the removal ofan asphaltene deposition in the oil reservoir, which may increase therecovered oil yield, quality, and purity. Reducing, removing,preventing, and/or mitigating an asphaltene deposition may desirablyprovide for the reduction and/or avoidance of plugging or clogging ofpores and may maintain open flow pathways to the production well,thereby permitting an increased ability for extraction of the oil withinthe reservoir.

The extraction process described above 100 may be performed in batchinjections, continuous injections, or combinations thereof.Additionally, solvent injection methods, injection pressures, and ratesmay be adjusted periodically or instantaneously depending on the oilrecovery yield from the oil reservoir.

The first solvent and the second solvent from the process above 100 maybe chosen for ease of use, recyclability, commodity price, andavailability. For example, the first solvent may include a lighthydrocarbon such as a methane, an ethane, a propane, a butane, apentane, a hexane, and combinations thereof. Use of a hydrocarbonsolvent comprising a propane as a first solvent in an extraction processmay provide for an in situ de-asphalting of an oil, which may providefor a production of a commercially enhanced product for sales.

The second solvent may be a non-petroleum based “green” solvent. Forexample, the non-petroleum based green solvent may be derived from aprocessed biomass or be a by-product of a wood, a pulp, a paperindustry, or a combination thereof. The second solvent may includebiomass based terpenes such as limonene. The second solvent may includea terpene or combination of terpenes, a turpentine, an alcohol, anaromatic hydrocarbon, or a combination thereof. Terpenes may behemiterpenes, monoterpenes, sesquiterpenes, diterpenes, triterpenes,tetraterpenes, and combinations thereof. Alcohols may be methanol,ethanol, propanol, isopropanol, butanol, and combinations thereof. Anaromatic hydrocarbon may be a benzene, a toluene, a xylene, andcombinations thereof.

The second solvent may include a diverting agent, which may desirablyprovide for a stimulation of the oil reservoir, which may provide for auniform injectivity profile of the second solvent in comparison to acorresponding second solvent not having the diverting agent. Thediverting agent may be a viscous surfactant, a polymer, a CO₂, orcombinations thereof. An extraction process comprising a diverting agentmay desirably provide for an increase in a sweep efficiency, an increasein a yield of recovered oil, or a combination thereof in comparison to acorresponding extraction process not having the diverting agent. Theconcentration of diverting agent in the second solvent may range fromabout 1% to about 50%, by volume of the second solvent. For example, asecond solvent may comprise a CO₂ at a concentration of about 10%, byvolume of the second solvent.

The first and second solvents may have the same or differentviscosities. For example, the second solvent may have a higher viscositythan the first solvent, which may desirably provide for an increasedrecovered oil percentage than extraction processes using a secondsolvent comprising a lower viscosity than the first solvent. In thiscase, using the less viscous first solvent to establish a communicationbetween the injection well and the production well, followed by aninjection of the more viscous second solvent may compensate forchanneling tendencies in the oil reservoir formation. Additionally, itmay be possible to ensure that deposition of asphaltene is mitigated anda high percentage of the oil is contacted and recovered.

FIG. 2 illustrates a system 200 for extracting oil from an oilreservoir. The system 200 includes a first solvent reservoir 210, aninjection well 230, a second solvent reservoir 220, an oil reservoir240, a production well 250, production treating facility 255, and arecovered oil reservoir 280. The production treating facility 255 mayseparate first solvent(s) from a first recovered oil, separate waterfrom the first recovered oil, separate second solvent(s) from the secondrecovered solvent and oil mixture, separate water from the secondrecovered solvent and oil mixture, distill recovered solvents, recyclethe first solvent, recycle the second solvent, distill recovered oil,purify recovered oil, and combinations thereof.

In the above described system 200, the injection well 230 is connectedto the first solvent reservoir 210 through a first solvent stream 215.The injection well 230 is connected to the second solvent reservoir 220through a second solvent stream 225. The oil reservoir 240 is connectedto the injection well 230 through an injection stream 235. Theproduction well 250 is connected to the oil reservoir 240 through arecovery stream 245. Optionally, the production treating facility 255may be connected to the second solvent reservoir 220 through a secondsolvent recycle stream 260. Optionally, the production treating facility255 may be connected to the first solvent reservoir 210 through a firstsolvent recycle stream 270. The production treating facility 255 may beconnected to the production well(s) 250 through the oil recovery stream265. The recovered oil reservoir 280 may be connected to productiontreating facility 255 through a recovered oil stream 275.

Additionally, in the system 200 described above, the injection well 230is configured to receive a first solvent from the first solventreservoir 210 through the first solvent stream 215. The injection well230 is configured to receive a second solvent from the second solventreservoir 220 through the second solvent stream 225. The productiontreating facility 255 is configured to receive an oil recovery stream265 from the production well(s) 250. The recovered oil reservoir 280 isconfigured to receive a recovered oil from the production treatingfacility 255 through a recovered oil stream 275. The first solventreservoir 210 is configured to receive a recycled first solvent from theproduction treating facility 255 through the first solvent recyclestream 270. The second solvent reservoir 220 is configured to receive arecycled second solvent from the production treating facility 255through the second solvent recycle stream 260. In some embodiments, thesystem 200 may comprise a surface processing facility. The surfaceprocessing facility may derive water from the recovered oil, may recyclesolvent, may refine recovered oil, and combinations thereof. A systemmay be configured to suit the situation and improve the results of theprocess. For example, components of the system may be adjusted includingvertical spacing of components, horizontal spacing of components, lengthin between components, length of system, relative elevation of the oilreservoir, vertical displacement of the production well(s), verticaldisplacement of the injection well(s), and combinations thereof.

As will be understood by those skilled in the art who have the benefitof the instant disclosure, other equivalent or alternative compositions,devices, processes, methods, and systems for extracting an oil form anoil reservoir comprising a mobile water can be envisioned withoutdeparting from the description contained herein. Accordingly, the mannerof carrying out the disclosure as shown and described is to be construedas illustrative only.

Persons skilled in the art may make various changes in the shape, size,number, and/or arrangement of parts without departing from the scope ofthe instant disclosure. For example, the position and number of solventsand extractions may be varied. In some embodiments, solvents may beinterchangeable. In addition, the size of a device and/or system may bescaled up or down to suit the needs and/or desires of a practitioner.Each disclosed process, method and method step may be performed inassociation with any other disclosed method or method step and in anyorder according to some embodiments. Where the verb “may” appears, it isintended to convey an optional and/or permissive condition, but its useis not intended to suggest any lack of operability unless otherwiseindicated. Where open terms such as “having” or “comprising” are used,one of ordinary skill in the art having the benefit of the instantdisclosure will appreciate that the disclosed features or stepsoptionally may be combined with additional features or steps. Suchoption may not be exercised and, indeed, in some embodiments, disclosedsystems, compositions, apparatuses, and/or methods may exclude any otherfeatures or steps beyond those disclosed herein. Elements, compositions,devices, systems, methods, and method steps not recited may be includedor excluded as desired or required. Persons skilled in the art may makevarious changes in methods of preparing and using a composition, device,and/or system of the disclosure.

Also, where ranges have been provided, the disclosed endpoints may betreated as exact and/or approximations as desired or demanded by theparticular embodiment. Where the endpoints are approximate, the degreeof flexibility may vary in proportion to the order of magnitude of therange. For example, on one hand, a range endpoint of about 50 in thecontext of a range of about 5 to about 50 may include 50.5, but not 52.5or 55 and, on the other hand, a range endpoint of about 50 in thecontext of a range of about 0.5 to about 50 may include 55, but not 60or 75. In addition, it may be desirable, in some embodiments, to mix andmatch range endpoints. Also, in some embodiments, each figure disclosed(e.g., in one or more of the examples, tables, and/or drawings) may formthe basis of a range (e.g., depicted value +/− about 10%, depicted value+/− about 50%, depicted value +/− about 100%) and/or a range endpoint.With respect to the former, a value of 50 depicted in an example, table,and/or drawing may form the basis of a range of, for example, about 45to about 55, about 25 to about 100, and/or about 0 to about 100.Disclosed percentages are volume percentages except where indicatedotherwise.

All or a portion of a system for extraction and recovery of oil fromreservoirs containing mobile water may be configured and arranged to bedisposable, serviceable, interchangeable, and/or replaceable. Theseequivalents and alternatives along with obvious changes andmodifications are intended to be included within the scope of thepresent disclosure. Accordingly, the foregoing disclosure is intended tobe illustrative, but not limiting, of the scope of the disclosure asillustrated by the appended claims.

The title, abstract, background, and headings are provided in compliancewith regulations and/or for the convenience of the reader. They includeno admissions as to the scope and content of prior art and nolimitations applicable to all disclosed embodiments.

EXAMPLES

Some specific example embodiments of the disclosure may be illustratedby one or more of the examples provided herein.

Example 1 Mobile Water Compared to Immobile Water Start-Up Comparison at10 m Apart

In a heavy oil reservoir that is oil wet, a solvent cocktail was used todisplace oil. In this example, one production well was placed betweentwo injection wells and the distance between injection well andproduction well was 10 m. The recovery factors with and without mobilewater present are shown in FIG. 3.

Example 2 Mobile Water Compared to Immobile Water Start-Up Comparison at40 m Apart

In a heavy oil reservoir that is oil wet, a solvent cocktail was used todisplace oil. In this example one production well was placed between twoinjection wells and the distance between each injection well andproduction well was 10 m. The recovery factors with and without mobilewater present are shown in FIG. 4. As shown in FIG. 4, increasing thedistance between the injector and the producer from 10 m to 40 m makesproduction less feasible unless mobile water is present.

Example 3 Solvent Composition Compared to Optimal Well Configuration

In a similar scenario as in Example 1, production acceleration andimproved sweep efficiency can be reached if the producer is augmented bythe injection of a second producer at a different depth (higher or lowerin the formation depending on the solvent cocktail composition). Thisadditional well may create new displacement pathways and may improvesweep efficiency by order of magnitude in respect to time. As shown inFIG. 5, employing a staggered well configuration may provide for adesirable oil recovery.

Well placement near a water/oil interface may allow fast spreading of asolvent and may allow access to very large volumes of oil. This mayaccelerate production and may be an advantageous option compared to aVAPEX type process.

Example 4 Thief Water Zone Presence

As shown in FIGS. 6A and 6B, the presence of a water thief zone may betaken advantage of to carry the solvent from injector to producer, addoil/solvent contact and accelerate oil production. In such cases it isanticipated that the production of water will be higher than previouscases.

What is claimed is:
 1. An extraction process for recovering oil from anoil reservoir comprising mobile water, the extraction processcomprising: (a) establishing at least one injection well and at leastone production well; (b) injecting a first solvent into the oilreservoir through the at least one injection well to form a firstmixture, the first mixture comprising the first solvent, a first portionof mobile water, and a first portion of oil, wherein the first solventcomprises a light hydrocarbon selected from the group consisting of amethane, an ethane, a propane, a butane, a pentane, a hexane, andcombinations thereof; (c) recovering the first mixture from the at leastone production well to produce a first recovered oil mixture, the firstrecovered oil mixture comprising the first solvent, the first portion ofthe mobile water, and the first portion of oil; (d) separating the firstrecovered oil mixture to produce a first recovered oil fraction that isseparated from the first portion of mobile water and the first solvent;and (e) injecting a second solvent into the oil reservoir through the atleast one injection well to form a second mixture, the second mixturecomprising the second solvent, a second portion of mobile water, and asecond portion of oil, wherein the second solvent comprises anon-petroleum based solvent selected from the group consisting of aterpene, a limonene, a hemiterpene, a monoterpene, an alcohol, asesquiterpene, a diterpene, a triterpene, a tetraterpene, andcombinations thereof.
 2. The extraction process according to claim 1,further comprising (f) recovering the second mixture from the at leastone production well to produce a second recovered oil mixture, thesecond recovered oil mixture comprising the second solvent, the secondportion of the mobile water, and the second portion of oil
 3. Theextraction process according to claim 2, further comprising (g)separating the second recovered oil mixture to produce a secondrecovered oil fraction that is separated from the second portion ofmobile water and the second solvent.
 4. The extraction process accordingto claim 1, wherein one or more of the first solvent further compriseswater and the second solvent comprises water.
 5. The extraction processaccording to claim 3, further comprising combining the first recoveredoil mixture and the second recovered oil mixture to produce a combinedrecovered oil mixture, wherein the combined recovered oil fractioncomprises a yield of about 50% to about 90% of the oil present in theoil reservoir prior to the extraction process.
 6. The extraction processaccording to claim 1, wherein one or more of: the first solvent is at atemperature from about 10° C. to about 40° C. during the step ofinjecting the first solvent into the oil reservoir through the at leastone injection well, and the second solvent is at a temperature fromabout 10° C. to about 40° C. during the step of injecting the secondsolvent into the oil reservoir through the at least one injection well.7. The extraction process according to claim 5, wherein the water ispresent at a concentration from about 0.1% to about 50%, by volume ofthe first solvent.
 8. The extraction process according to claim 1,further comprising injecting the separated first solvent into the oilreservoir through the at least one injection well to form a combinedseparated first solvent and oil mixture.
 9. The extraction processaccording to claim 3, further comprising injecting the separated secondsolvent into the oil reservoir through the at least one injection wellto form a combined separated second solvent and oil mixture.
 10. Theextraction process according to claim 1, further comprising injectingwater into the oil reservoir through the at least one injection well toform an injected water and oil mixture.
 11. The extraction processaccording to claim 10, wherein the water comprises a water exogenous tothe oil reservoir.
 12. The extraction process according to claim 10,wherein injecting water into the oil reservoir through the at least oneinjection well is performed after the injecting the second solvent intothe oil reservoir through the at least one injection well.
 13. Theextraction process according to claim 3, further comprising: (h) addinga third solvent selected from the group consisting of CO₂, and N₂, intothe oil reservoir through the at least one injection well; (i) shuttingthe oil reservoir for a time of from about 1 day to about 7 days to forma combined third solvent and second residual oil mixture; and (j)opening the oil reservoir; and recovering at least a portion of thethird solvent and second residual oil mixture from the at least oneproduction well to produce a recovered third solvent and second residualoil mixture.
 14. The extraction process according to claim 3, whereinsteps (a) to (g) are repeated at least once.
 15. The extraction processaccording to claim 1, wherein both the first solvent and the secondsolvent are simultaneously injected through the at least one injectionwell.
 16. An extraction system for extracting and recovering an oil froman oil reservoir comprising mobile water, the extraction systemcomprising: (a) at least one injection well connected to the oilreservoir through an injection stream; (b) at least one production wellconnected to the oil reservoir through a recovery stream; (c) a firstsolvent reservoir connected to the injection well through a firstsolvent stream, wherein the injection well is configured to receive afirst solvent from the first solvent reservoir through the first solventstream, and wherein the first solvent comprises a light hydrocarbonselected from the group consisting of a methane, an ethane, a propane, abutane, a pentane, a hexane, and combinations thereof; and (d) a secondsolvent reservoir connected to the injection well through a secondsolvent stream, wherein the injection well is configured to receive asecond solvent from the second solvent reservoir through the secondsolvent stream, and wherein the second solvent comprises a non-petroleumbased solvent selected from the group consisting of a terpene, alimonene, a hemiterpene, a monoterpene, an alcohol, a sesquiterpene, aditerpene, a triterpene, a tetraterpene, and combinations thereof. 17.The extraction system of claim 16, further comprising: (e) a productiontreating facility connected to the production well through an oilrecovery stream, wherein the production treating facility is configuredto receive a first solvent and oil mixture and a second solvent and oilmixture from the production well; and (f) a recovered oil reservoirconnected to the production well through the oil recovery stream,wherein the recovered oil reservoir is configured to receive a recoveredoil from the production treating facility through a recovered oilstream.
 18. The extraction system of claim 17, wherein the first solventreservoir is connected to the production treating facility through afirst solvent recycle stream, and wherein the first solvent reservoir isconfigured to receive a recycled first solvent from the productiontreating facility through the first solvent recycle stream.
 19. Theextraction system of claim 17, wherein the second solvent reservoir isconnected to the production treating facility through a second solventrecycle stream, and wherein the second solvent reservoir is configuredto receive a recycled second solvent from the production treatingfacility through the second solvent recycle stream.
 20. An extractionprocess for recovering oil from an oil reservoir comprising mobilewater, the extraction process comprising: (a) establishing at least oneinjection well and at least one production well; (b) injecting a firstsolvent into the oil reservoir through the at least one injection wellto form a first mixture, the first mixture comprising the first solvent,a first portion of mobile water, and a first portion of oil, wherein thefirst solvent comprises a non-petroleum based solvent selected from thegroup consisting of a terpene, a limonene, a hemiterpene, a monoterpene,an alcohol, a sesquiterpene, a diterpene, a triterpene, a tetraterpene,and combinations thereof; (c) recovering the first mixture from the atleast one production well to produce a first recovered oil mixture, thefirst recovered oil mixture comprising the first solvent, the firstportion of the mobile water, and the first portion of oil; (d)separating the first recovered oil mixture to produce a first recoveredoil fraction that is separated from the first portion of mobile waterand the first solvent; and (e) injecting a second solvent into the oilreservoir through the at least one injection well to form a secondmixture, the second mixture comprising the second solvent, a secondportion of mobile water, and a second portion of oil, wherein the secondsolvent comprises a light hydrocarbon selected from the group consistingof a methane, an ethane, a propane, a butane, a pentane, a hexane, andcombinations thereof.